Ensure that CameraHalDispatcher::RegisterClient runs on the right thread

In crrev.com/c/1687018 we added a local call site to RegisterClient, so
we can no longer assume the method is always called through Mojo IPC.

      enabled.

Bug: 1000842
Test: Make sure Chrome debug build starts on Nocturne with ARC++
Change-Id: Ibe546396646bab01c7caec02ff72f8122ac80181
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1817875Reviewed-by: Wei Lee <wtlee@chromium.org>
Reviewed-by: Shik Chen <shik@chromium.org>
Commit-Queue: Ricky Liang <jcliang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699208}

media/capture/video/chromeos/camera_hal_dispatcher_impl.cc

@@ -186,14 +186,13 @@ void CameraHalDispatcherImpl::RegisterServer(
 
 void CameraHalDispatcherImpl::RegisterClient(
     cros::mojom::CameraHalClientPtr client) {
-  DCHECK(proxy_task_runner_->BelongsToCurrentThread());
-  auto client_observer =
-      std::make_unique<MojoCameraClientObserver>(std::move(client));
-  client_observer->client().set_connection_error_handler(base::BindOnce(
-      &CameraHalDispatcherImpl::OnCameraHalClientConnectionError,
-      base::Unretained(this), base::Unretained(client_observer.get())));
-  AddClientObserver(std::move(client_observer));
-  VLOG(1) << "Camera HAL client registered";
+  // RegisterClient can be called locally by ArcCameraBridge. Unretained
+  // reference is safe here because CameraHalDispatcherImpl owns
+  // |proxy_thread_|.
+  proxy_task_runner_->PostTask(
+      FROM_HERE,
+      base::BindOnce(&CameraHalDispatcherImpl::RegisterClientOnProxyThread,
+                     base::Unretained(this), client.PassInterface()));
 }
 
 void CameraHalDispatcherImpl::GetJpegDecodeAccelerator(
@@ -331,6 +330,19 @@ void CameraHalDispatcherImpl::StartServiceLoop(base::ScopedFD socket_fd,
   }
 }
 
+void CameraHalDispatcherImpl::RegisterClientOnProxyThread(
+    mojo::InterfacePtrInfo<cros::mojom::CameraHalClient> client_ptr_info) {
+  DCHECK(proxy_task_runner_->BelongsToCurrentThread());
+  cros::mojom::CameraHalClientPtr client_ptr(std::move(client_ptr_info));
+  auto client_observer =
+      std::make_unique<MojoCameraClientObserver>(std::move(client_ptr));
+  client_observer->client().set_connection_error_handler(base::BindOnce(
+      &CameraHalDispatcherImpl::OnCameraHalClientConnectionError,
+      base::Unretained(this), base::Unretained(client_observer.get())));
+  AddClientObserver(std::move(client_observer));
+  VLOG(1) << "Camera HAL client registered";
+}
+
 void CameraHalDispatcherImpl::AddClientObserverOnProxyThread(
     std::unique_ptr<CameraClientObserver> observer) {
   DCHECK(proxy_task_runner_->BelongsToCurrentThread());

media/capture/video/chromeos/camera_hal_dispatcher_impl.h

@@ -93,6 +93,8 @@ class CAPTURE_EXPORT CameraHalDispatcherImpl final
   // Runs on |blocking_io_thread_|.
   void StartServiceLoop(base::ScopedFD socket_fd, base::WaitableEvent* started);
 
+  void RegisterClientOnProxyThread(
+      mojo::InterfacePtrInfo<cros::mojom::CameraHalClient> client_ptr_info);
   void AddClientObserverOnProxyThread(
       std::unique_ptr<CameraClientObserver> observer);